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GCN Circular 21632

LIGO/Virgo G298048: Continued monitoring of the optical counterpart candidate
2017-08-21T15:49:41Z (7 years ago)
Myungshin Im at Seoul National U <>
M. Im, C. Choi, J. Kim, Lim, G. H. M. Lee (SNU), S.-L. Kim, C.-U. Lee
(KASI) on behalf of the KU collaboration

We continued to monitor the strong optical counterpart candidate of
LIGO/Virgo G298048 (GCNs 210505, 21509, 21513), SSS17a/DLT17ck(Coutler et
al. GCN 21529; Allam et al. GCN 21530; Yang et al. GCN 21531; Arcavi et al.
GCN 21538; also see notes below for a list of optical/NIR observation
reports). The observation was carried out using three KMTNet 1.6m
telescopes and other small telescopes (Im et al. GCNs 21563, 21566, 21597)
at three sites , the Siding Spring Observatory (SSO), the South African
Astronomical Observatory (SAAO), and the Cerro-Tololo Inter-American
Observatory (CTIO). We imaged the object with B,V,R,I,i,z, filters and
medium-band images at 825, 875, 925, 975 nm.

We confirm that the object is fading in optical and its continuum shape has
been becoming redder as time goes on (e.g., Cenko et al. GCN 21572; Lyman
et al. GCN 21582; Wiseman et al. GCN 21584; Chambers et al. GCN 21590;
Malesani et al. GCN 21590; Chen et al. GCN 21608). A part of the data from
several sites are presented below.

UT V R I Site

08-18.72 17.8(0.1) 17.4(0.1) 17.3(0.1) SAAO

08-18.99 18.3(0.1) 17.6(0.1) 17.4(0.1) CTIO

08-19.72 19.4(0.1) 18.3(0.1) 17.9(0.1) SAAO

08-19.98 19.8(0.1) 18.4(0.1) 18.2(0.1) CTIO

The observations and further analysis of the data are ongoing.

Notes: It is remarkable that more than 40 optical/NIR follow-up
imaging/spectroscopic observations of the optical counterpart candidates
have been reported in three days since the first discovery report of the
optical counterpart. For reference, we list them here (let me know if I am
missing any). They are, Coutler et al. (GCN 21529, 21567), Allam et al.
(GCN 21530), Yang et al. (GCNs 21531, 21579), Melandri et al. (GCN 21532,
21596), Arcavi et al. (GCNs 21538, 21565, 21581), Nicholl et al. (GCN
21541, 21580, 21585), Tanvir et al. (GCN 21544), Lipunov et al. (GCNs
21546, 21570, 21587), Drout et al. (GCN 21547), Evans et al. (GCN 21550),
Simon et al. (GCN 21551), Singer et al. (GCN 21552), Chambers et al. (GCN
21553, 21590, 21617), Wolf et al. (GCN 21560), Yoshida et al. (GCN 21561,
21586), Im et al. (GCNs 21563, 21566, 21597), Cenko et al. (GCN 21572),
Lyman et al. (GCN 21582), Kilpatrick et al. (GCN 21583), Wiseman et al.
(GCN 21584), Malesani et al. (GCN 21591), D���Elia et al. (GCN 21592),
Wiersema et al. (GCN 21594), Tominaga et al. (GCN 21595), Valenti et al.
(GCN 21606), Chen et al. (GCN 21608), Pozanenko et al. (GCN 21618), Nakaoka
et al. (GCN 21623), Castro-Tirado et al. (GCN 21624), Coward et al. (GCN
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